This invention concerns surgical microscopes having two optomechanically coupled observation barrels at least one of which is arranged to be relatively rotatable about the optical axis of the other. Each observation barrel is provided with its own respective magnification system, while both share a common observation path to the object field through an optical beam splitter.
Such microscopes are needed in modern surgery to permit two surgeons to observe simultaneously the same field of vision under the same angle of view. Preferably, the second observation barrel should be appropriately oriented 90.degree. offset from the first, being positionable selectively to either the right or to the left of the barrel being used by the principal surgeon.
For many demanding surgical techniques, it is necessary that the microscope's illumination beam be directed along an axis as nearly coincident as possible with the axis of the reflected observation beam, and one known arrangement of optomechanically coupled surgical microscopes for two surgeons does provide such coaxially-directed illumination. This arrangement is shown in commonly assigned British Patent No. 2 146 789 A. However, each of the two coupled surgical microscopes disclosed in this British reference has its own respective illumination source and its own respective objective lens, and these optical systems are joined below their respective objective lenses through a common optical splitter system. This prior art arrangement results in blooming and interfering light reflections which occur as the illuminating beam passes through one or the other of these respective main lenses.